Pressure- and temperature-controlled crystal growing apparatus

ABSTRACT

Furnace assembly providing a working volume the pressure in which may range from 10 5 torr to 100 atmospheres. Controlled temperatures up to 4,000* C. are attainable. Two load-bearing rods extending into the furnace are rotated and moved along their vertical axes over a wide speed range. Means are provided continuously to indicate the precise position of each rod, to monitor the operation within the furnace by TV, and to control the operations within the furnace from a remote location.

U Umted States Patent [is] 3,639,718 Castonguay et al. 1 Feb. 1, 1972 [54] PRESSURE- AND TEMPERATURE- 3,410,945 l1/l968 Regner et a1 ..13/1 CONTROLLED CRYSTAL GROWING 2,972,525 2/1961 Emeis 219/1043 APPARATUS 2,893,847 7/1959 Schwerckert et al .....2l9/l0.43 3,493,770 2/ 1970 Dessauer ..23/273 SP [72] Inventors: Roger A. Castonguay, Salem; Bernard C.

Henley, Chestnut Hill; Francis J. Mal- Primary Examiner-R. F. Staubly l Woburn; J ph Wenckus, Need- Assistant Examiner-Hugh D. Jaeger ham, all of Mass. Attorney-Bessie A. Lepper [73] Assignee: Arthur D. Little, Inc., Cambridge, Mass.

[57] ABSTRACT [22] Filed: June 15, 1970 Furnace assembly provrding a working volume the pressure in PP ,096 which may range from 10" torr to I atmospheres. Controlled temperatures up to 4,000" C. are attainable. Two load- 152 us. 01 ..219/l0.67, 13/ 1, 13/31, bearing rods extending the furnace are routed and 219/1043 along their vertical axes over a wide speed range. Means are [51 J Int. Cl. ..Hb 5/110 Provided continuously to indicate the Precise Position of each [58] Field of Search ..13/31, 1; 219/1043, 10.77, to monitor the operation within the furnace y TV, and to 219/1057 1043; 23/273 Sp control the operations within the furnace from a remote location. [5 6] References 20 Claims, 18 prswin Figures UNITED STATES PATENTS 3,211,881 /1965 Jablonski ..219/10.43 X

165 4 284 293 I63 289 124 154 I57 I 1690 155 7' l23 5 s- 1 13a 17 I I22 '4' 153 s a 93 r 121 2 159 3 129 151 s 30 l '3' Isl 94 102 137 '3' I71 162 34 '42 12a 5 I26 7 131; 27 133 27 135 9 M5 o I 173 I27 I 146 25 I 114 i 35 33 I no l l69b 132 112 -l92 manna m nan SHEET UlflF 11 90 ooonooo l/WE/WORS Roger A Cas'ronguay Bernard C. Hanley Francis J. Mallahon Joseph F. Wenckus /3 --4 fl.

Horney PATENIEDFEB H972 3.639319 SHEEI 0 40f 11 //VVE/V70/P$ Roger A. Cas'ronguay Bernard C. Honley Francis J. Mallaho'n Joseph F. Wenckus Arrorney PATENIEBFEB 11972 1 39.718 SHEET 050? 11 IM EIWORS Roger A Ccsfonguay Bernard C. Hunley Francis J. Mallahan B Joseph F. Wenckus PATENIED FEB H972 SHEET 06 0F 11 //l VE/V7'0/?S Roger A. Cosfonguay Bernard C Hanley P us Francis J. Mallahan B Joseph F. Wenckus /Z-w' A forney SHEEI 08 0F 11 PATENIEBFEB H97? PATENTEBFEI H972 3.639.718

suzn user 11 IIVVf/VTORS Roger A. Costonguay Bernard C. Henley Francis J Molluhan Joseph F. Wenckus fromey mentions H912 sum 10 or 11 Attorney REVERSIBLE 221 ELECTRO- MAGNETIC 371 44 COUNTER $7 E 5; m5} FLEXIBLE 224 g SHAFT 369 DRIVING MECHANISM no. Ran; CONTROL 40/ MOTOR 372 A. c. SUPPLY Fug. 16

AC 11 INPUT I I v 377 376 PROPORTIONAL E AZE E MAGNETIC E TEMPERATURE REACTOR AMPLIFIER CONTROL SYSTEM VOLTS INDUCTION SIGNAL HEATING POWER 375 SUPPLY RADIAMATIC PYROMETER I PYROMETER UVVE/VTORS Roger A. Cusfonguuy Bernard C. Henley Francis J. Mollchun y Joseph F. wenckus PATENTEDm H972 3539.17.15

SHEET 110E 11 /315 r Ti 1 l I I ac. MOTOR 385 3 5 CONTROL 1 1 0.0. A.C. /315 CLUTCH C L POWER 392 187 SUPPLY 42\\ SPEED A.C. MOTOR 96 I80 1 8 j 197 A.C. ,44

| 0.0. SUPPLY \i 1 CLUTCH 388 Mofi'dR 8 391 ses CONTROL fig 390 ,3? J A.C. J L

31s A Flg. 18

m/vmroes Roger A. Cusronguoy Bernard C. Henley Francis J. Mallohon 5y Joseph F. Wenckus PRESSURE- AND TEMPERATURE-CONTROLLED CRYSTAL GROWING APPARATUS This invention relates to an apparatus for growing crystals and more particularly to an apparatus for growing crystals under controlled atmospheric pressures from -5 torr to 100 atmospheres and at temperatures up to 4,000 C.

An apparatus suitable for growing many different types of crystals is required to be able to furnish many different controlled conditions. For example, the growing of crystals of a III-V intermetallic compound may require that a very high pressure be maintained around the growing crystal area to control the vaporization of a volatile component such as arsenic or phosphorus in forming an intermetallic arsenide or phosphide. In other crystal-growing processes it is necessary to supply a moderate to high vacuum. Thus a general-process multipurpose crystal growing apparatus should be capable of growing crystals of oxides, salts, metals, semiconductors including the phosphides, arsenides, tellurides, selenides and sulfides and any other inorganic element, compound or mixtures thereof. Moreover, such a furnace should be capable of operating in one of several crystal-growing techniques including the vertical pulling or Czochralski, the temperaturegradient or Bridgman-Stockbarger and the floating-zone techniques.

It is therefore, a primary object of this invention to provide crystal-growing apparatus which may be used over a pressure range from as low as 10 5 torr to as high as NO atmospheres and at temperatures up to 4,000 C. It is another object of this invention to provide crystal-growing apparatus of the character described in which one of several different techniques for growing crystals including the Czochralski, Bridgman-Stockbarger, and floating-zone techniques may be performed. It is yet another object of this invention to provide such apparatus which is suitable for operation by remote control and remote observation, and which has built into it safety features which make the apparatus reliable to use under any extreme high vacuum or pressure and temperatures desired. It is yet another object of this invention to provide such an apparatus which permits rapid height adjustments of one or both pulling shafts before, during, and after the crystal-growing operation. Other objects of the invention will in part be ebvious and will in part be apparent hereinafter.

The invention accordingly comprises the features of construction, combinations of elements, and arrangements of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which FIG. 1 is a perspective view of the apparatus of this invention showing the furnace assembly in side view, the power supply and the operational console;

FIG. 2 is a front view of the furnace assembly of FIG. 1;

FIG. 3 is a top plan view of the furnace assembly of FIG. 1;

FIGS. 4, 5 and 6 are front, side, and cross-sectional views of the pressure sealing access port;

FIG. 7 is a cross section through the furnace shown in the Czochralski mode of operation;

FIG. 8 is a side view, partly in cross section, of the synchor- I nous drive assembly for the load-bearing rods which experience controlled-rate rotational and translational motions;

FIG. 9 is a perspective view of the rotational and translational driving mechanisms for the load-bearing rods;

FIG. [0 is a detailed cross-sectional view of the rotational and translational shaft driving mechanisms associated with the lower rod;

FIG. 11 is a cross-sectional view of the mechanism of FIG. 10 taken along line 11-11 ofthe figure;

FIG. 12 is a detailed cross section of the lower end of the lower rod;

FIG. 13 is a detailed cross section of the upper end of the lower rod;

FIG. 14 is a detail of the upper end of the upper rod showing the means for introducing and withdrawing a cooling liquid;

FIG. 15 is a diagram showing the flow of a liquid coolant around the furnace assembly;

FIG. 16 illustrates diagrammatically the mechanism for continuous readout of the positions of the load-bearing rods;

FIG. 17 illustrates diagrammatically the temperature control system; and

FIG. 18 illustrates diagrammatically the mechanism for selecting the load-bearing rods to be moved and the speed at which they are to be moved.

The crystal-growing apparatus of this invention comprises a pressure-sealed, water-cooled furnace; upper and lower loadbearing rods, capable of being rotated and moved along their axes, which operate within the furnace and extend beyond the furnace so that the driving mechanisms associated with them may be located outside the furnace; and a viewing port system which is suitable for accommodating a television camera for remote monitoring and controlling. The driving mechanisms may be alternatively operated in a slow, crystal-growing mode, or in a fast, rapid-positioning mode. Means are also supplied to monitor the temperature of the crystal-growing area, to interchange the heating means, to cool the upper shaft within the furnace and to determine precisely the position of each rod. A simple interchanging of several of the components carried by the load-bearing shafts and of some of the associated crystal-growing equipment pennits a choice of crystal-growing techniques. As a result the apparatus of this invention has a large number of degrees of freedom of operation including materials from which the crystals are grown, atmospheres, pressures and temperatures under which they are grown, the rate at which they can be formed, and the like.

The total apparatus is illustrated in a perspective view of FIG. 1. It will be seen to comprise a'fumace assembly 10, a power supply 11 and an operational console 12, the furnace being separated physically from the power supply and the operational console by a suitable barrier such as wall 13. Although the furnace assembly has been designed to meet the requirements of Section VIII of the ASME Pressure Vessel Codes, it is always desirable to locate such apparatus which is maintained at a high pressure remote from any operating personnel. As will be apparent in the following description the apparatus of this invention may be controlled and monitored from a remote location.

The furnace assembly is shown generally in outlet form in FIGS. 1 and 2, FIG. 1 being a side view, FIG. 2 a front view. This furnace assembly is seen to comprise the furnace 15, a pressure-sealed port 16, a primary viewing port 17 with which a TV camera 18, positioned on a TV support 19, may be associated so that the operation may view the crystal growing process on the TV screen 20 located on the operational console 12. An optional viewing port 21 may also be added.

Power for heating the crystal growing area is supplied by way of an RF power inlet conduit 25 pressure sealed to the furnace by a pressure-sealing flange 26. Through this flange 26 an RF cable 27 passes through a cable conduit 28 to be connected to the power supply 11.

The pressure maintained within the furnace may be monitored through a pressure or vacuum gauge 30 which is in communication with the power inlet conduit 25 through a gauge connection 31. For remote monitoring a second pressure gauge 29 is located on console 12. Communication between the interior of the furnace and a vacuum pump 32, such as an oil diffusion pump, is by way of a vacuum line 33 and a valve 34.

The load-bearing rods used within the furnace and their associated driving mechanisms are illustrated very generally in FIGS. 1 and 2 and will be described in detail with regard to FIGS. 7-14 presented below. The upper rod mechanism is generally indicated at 36 and the lower rod mechanism at 37. The upper motor 38 for imparting rotary motion to the upper rod and the lower motor 39 for imparting rotary motion to the lower rod, a drive synchronizer motor 40 (FIG. 3), gear box 41, high-speed motor 42, upper flexible shaft housing 43 and lower flexible shaft housing 44 are shown in FIGS. 1 and 2. As will be seen in these drawings the furnace assembly may be mounted on any suitable support such as the movable table 45 shown in these figures.

Associated with line 33 above valve 34 are a self-resetting pressurerelief valve 57 and a solenoid-actuated relief valve 58. A gas outlet line 59 controlled by valve 60 on the console is in fluid communication with the furnace interior through line 33.

Before describing the components of the furnace in greater detail it will be helpful for purposes of orientation to refer to FIG. 3 which is a top plan view of the furnace assembly. In this figure like components are referred to by like numerals used in FIGS. 1 and 2 and throughout the discussion and drawings. The drive synchronizer motor 40 is used to provide the power for the translational motion of the two load-bearing rods during the crystal growing operation; while the high-speed motor 42 is used to drive the rods at a high-speed rate at any desired time, and particularly for rapid positioning. A speed-control gear system 41, is used to provide the necessary control over the rate of translational motion of the shafts in their slow-motion operational mode; and the variable-speed synchronizer motor 40 is connected into the main, speed-control gear system by means of a gearing mechanism 48, coupling 49, shaft 50 and coupling 51. The speed-control gear system 41 and the high-speed motor 42 can be alternatively connected to shaft 52 as will be described below in conjunction with the description of FIG. 8. A pulley mechanism 53 furnishes the necessary mechanical connection between high-speed motor 42 and shaft 52. The shaft 52 in turn is connected through coupling 54 into the driving mechanism, generally indicated by reference numeral 55, which is designed to impart translational motion to the upper and lower rod mechanisms. The upper rod mechanism 36 is shown in FIG. 3 to be connected to this drive mechanism 55 through a flexible shaft 43 which is in turn connected to the upper load-bearing rod through a coupling attachment 56.

Figs-4, and 6 show front, side and cross-sectional views on the access port to ,the furnace which is closed by a hinged access port closure mechanism. The access port 64 (FIG. 6) provides direct access to the operator to install the desired fonn of heating unit, crystal-growing apparatus, raw material etc., within the interior of the furnace at the crystal-growing area. This port is sealed to make the volume within the furnace pressuretight by means of a hinged cover 65, the peripheral flange of which mates with a peripheral flange of the access port housing 66. A sealing ring 67 is used between the two flanges. The cover 65 is held by two supports 68 attached to a rod 69 which is rotatable around its axis and which is mounted through brackets 70 to the access port housing 66. Mechanical pressure between hinge cover 65 and the access port housing 66 is effected through two internally grooved semicircular rings 72 and 73, the internal grooves of which are configured to conform to the inclined surfaces of the flanges of the hinge cover 65 and the access port housing 66. Mechanical loading to resist internal pressure is accomplished through the use of bolts 74 and 75 which pass through central bushings 76 and 77. As the upper and lower bolts 74 and 75 are turned simultaneously the grooved flanges 72 and 73 are drawn together and are forced toward the center of the hinged cover 65 thus causing sealing ring 67 to form a seal between the flanges of the cover and housing. The access port is equipped with a pressure-relief valve 79 which prevents the operator from opening the furnace until the pressure within the furnace is essentially atmospheric.

The furnace is shown in a longitudinal cross section in FIG. 7. It will be seen that the furnace housing comprises an upper section 90, a central section 91, and a lower section 92 and defines within it a volume 93 which is the working area of the furnace. In FIG. 7 thefurnace and the pulling head are shown being used to form a crystal by the Czochralski technique. In this exemplary arrangement, the crucible containing the molten material fromwhich the crystal is to be formed remains stationary while the crystal boule is pulled upwardly attached to the upper pulling head 94 which in turn is affixed to the upper load-bearing rod 95. Comparable to the upper rod 95 is a lower rod 96 which supports a graphite susceptor 97 as well as a support ring 98 which is affixed to the shaft through a support collar 99. Resting on the support ring 98 is an inner quartz radiation shield 100. The crucible 101 containing the melt 102 used to form the crystal 104 is rested in the graphite susceptor 97 and may be covered with an encapsulating material 103 through which the crystal 104 is pulled.

In the exemplary mode of operation shown in FIG. 7 there is positioned around the inner quartz radiation shield a outer quartz radiation shield which is in the form of a deep well and which rests supported on a radiation shield support 111. A suitable bushing 112 permits the lower load-bearing rod 96 to pass through the bottom of the outer radiation shield and extend upwardly through the support collar 99 and into the graphite susceptor 97. Extending through the length of the lower rod 96 (which is hollow and which is sealed on its upper end) is a thermocouple shield 114 through which thermocouple wires I15 and 116 (FIG. 13) extend and meet to form a thermocouple junction 117 used to monitor the temperature of the graphite susceptor adjacent to the crucible. Extending through the two radiation shields 110 and 100 is a sapphire light pipe 120 which is suitable for connection to a radiamatic pyrometer positioned on the outside of the furnace chamber.

This mechanism provides a second temperature measuring means.

Heating is supplied to the crucible 101 by means of RF coil which is positioned around the outer radiation shield and which is connected through leads 126 and 127 to terminals located within a mating flange 128. The mating flange in turn is connected through proper terminals to the RF cable 27 which extends down through the power inlet conduit 25 and out through the RF flange 26 comprising a blind flange 129 forming a pressuretight seal with mating flange 130 of the power inlet conduit 25 through a O-ring 131, and the use of a plurality of bolts 132. A pressuretight seal must also of'course be fonned around RF cable 27 where it passes through RF flange 26 and it is illustrated in FIG. 7 to comprise an insulating member 133 and a Conaxtype pressure gland I34. The RF cable and the mating flange 128 are supported by means of an insulated collar 135 within the power inlet conduit 25. This arrangement permits various RF coils to be installed within the crystal-growing area and, if desired, it permits the use of a resistance heater. It is only necessary to unplug the terminals of leads 126 and 127 from the mating flange 128 to substitute a different heating assembly. As noted above, gage connection 31 provides means to connect a'vacuum or pressure gage to monitor the pressure in the furnace. A particle trap 35 is located in *the valve-controlled conduit 33 leading to the vacuum pump shown in FIGS. 2 and 3.

As pointed out above, the furnace illustrated in FIG. 7 is adapted for growing crystal by the Czochralski technique. It will of course be appreciated by anyone skilled in the art that the arrangement shown in FIG. 7 may be easily modified to use the temperature-gradient (Bridgman-Stockbarger) technique by moving the upper rod 95 to its topmost position out of the way and mounting a suitably designed crucible on the lower rod 96. This crucible will be configured to define a deep well which terminates at the bottom in a conical tip and is positioned within the RF coil for melting the crystal-forming material. Crystallization is then accomplished by rotating and moving the lower rod and its supported crystal downwardly beyond the limits of the RF coil.

It will also, of course, be apparent to those skilled in the art that the floating zone technique may also be used by attaching a pressed cylinder of the material to be formed into a crystal between upper and lower chucks attached to upper and lower rods 95 and 96 and then by simultaneously moving these rods to cause the pressed cylinder to rotate and to slowly pass through the heating area.

The-upper and lower rods extend beyond the interior of the furnace and are driven by mechanisms located external of the furnace volume 93. These rods 95 and 96 must therefore be provided with upper and lower bushing assemblies 284 and 285 which are described below in detail with reference to FIG. 10. It should be noted here that the two rods may be moved separately or simultaneously in a slow mode at predetermined rotational and translational speeds or in a rapid mode for quick positioning.

The primary viewing window 17 is positioned and aligned to permit a relatively wide view of the crystal-growing area within furnace volume 93. This primary viewing port is formed of a main housing 136 which is welded to the central section 91 of the furnace housing, and of a window cap ring 137 which is affixed to the main window housing by means of a plurality of screws one of which is shown at 138. The viewing port 139 is defined within the cap ring 137. The window housing and cap ring are so configured as to define between them a circular recess in which a tempered Pyrex window 140 is held. The seal between the window surface and the main housing is made through an O-ring 142. The internal pressure load on window 140 is carried through elastomeric washer 141 to window cap ring 137. In order to protect the Pyrex window and control the optical character of the image transmitted through it there is interposed between window 140 and the crystalgrowing area an adjustable infrared-reflecting window 143 which serves to reduce the axial temperature gradient on window 140. This window 143 is held in an annular mounting ring 144 rotatable within the main housing 136 by virtue of the screw thread arrangement. A cross-polarizer 121 is rotatably mounted in frame 122 on the cap ring 137. Its purpose is to control the intensity of the image transmitted through window 140.

Gas for flushing out the furnace or for pressurizing it is introduced by way of a gas line 145 which is so positioned as to cause the incoming gas to impinge upon the exposed surface of the polarizing radiation shield 143. This makes it possible to clean the window whenever necessary. The gas flow is controlled through a valve 146 which provides the communication between line 145 and the gas supply conduit 147 which leads to a gas supply not shown.

The auxiliary viewing port 21, designed to provide a-more restricted view into the crystal-growing area from a different angle, is constructed in substantially the same manner. Since use of the auxiliary viewing port is an optional feature, no opening in the central section 91 is made unless the auxiliary port is desired, in which case there is provided an auxiliary viewing port adapter 151 which communicates with the volume 93 within the furnace. In FIG. 7 the auxiliary viewing port is, however, shown attached to the adapter. It will be seen to comprise a window housing support 152 and a window housing cap 153. The tempered Pyrex window 156 is mounted in a similar fashion as window 140 through the use of an elastomeric washer 157 and an elastomeric O-ring 158. This window also has an infrared-reflecting window 159 associated with it and it has an external cross-polarizer 123 rotatably mounted in frame 124. As in the case of the primary viewing port a gas line 160 is positioned to cause gas to impinge on the exposed surface of the radiation shield. Flow of gas against the shield and into the system is controlled through valve 161 which provides the necessary fluid communication between line 160 and gas supply line 162. In addition to valves 146 and 161, the gas flow into the furnace is also remotely controllable by valve 148 on console 12 (Fig. 1).

Extensive means are provided to cool the furnace assembly. The entire cooling means is illustrated diagrammatically in FIG. 15. In FIG. 7 a portion of the coil system for circulating a suitable coolant such as water will be seen. In the upper and lower bushing assemblies 284 and 285 there are provided annular channels 163 and 164, respectively. These are adapted to be connected through connections 16S and 166 to a water supply line 167 (FIG. Cooling coils are wrapped in heat exchange relationship to the outside walls of the furnace components. Thus coil 169a is associated with the upper furnace housing 90, coil 170 with the auxiliary viewing port 21, coil 171 with the RF conduit 25, coil 1691: with the central furnace housing 91, coil 172 with the access port 16 (FIG. 5), coil 173 with the main viewing port 17 and coil 169c with the lower furnace housing 92. As will be seen in FIG. 15, the coils are two fluid conduits wound in parallel as indicated by the solid and dotted lines. These are joined by a loop 174 which has two valve-controlled connections 174a and 17412. The coolant may be introduced into one side of the parallel coils such as by a suitable line (not shown) joined through connection 188 and withdrawn through the other side of the coils such as by a suitable line (not shown) joined through connection 189. Alternatively, some or all of the coolant may be withdrawn through a line attached to connection 174a and fresh or additional coolant added through a line attached to connection 174b. This alternative arrangement provides flexibility in the manner in which the furnace assembly may be cooled.

Translational and rotational motions of the two load-bearing rods 95 and 96 are achieved through the mechanism illustrated in detail in FIGS. 8-11. Reference should also be had to FIG. 3 in which like numbers are used to refer to like components. In order to drive one or both of the rods 95 and 96 in the crystal-growing slow mode or in the quick-positioning rapid mode it is necessary to provide a mechanism for switching from one of these modes to the other and for insuring that when the switch is made the mode not selected is automatically disengaged. The mechanism for achieving this is illustrated in detail in FIG. 8 as well as in top plan view in FIG.

In FIG. 8 the shaft 50 and its associated couplings which connect the gearing mechanism 48 associated with sychronizing drive motor 40 to the speed-control gearing mechanism 41 have been omitted for simplicity of presentation. These components may be seen however in FIG. 3. The crystal-growing or slow-driving mode is achieved through connecting the flexible driving shafts 43 and 44 (associated with upper and lower rods, respectively) with the shaft 52, the speed of rotation of which is determined by proper selection of the gears in speedcontrol gear assembly 41 and adjusting the speed of motor 40. Shaft 52 is connected to the flexible shafts 43 and 44 through a magnetic clutch 175 which in turn is used to drive a shaft 176 when engaged. Shaft 176 in turn is coupled to a bevel or right-angle drive 177 and is made up of the worm gears 178, 179 and 180, the combination of gears 178 and 179 being used to drive the flexible shaft 43 which is associated with the upper load-bearing rod 95 and the combination of gears 178 and 180 being associated with the flexible shaft 44 used to drive the lower load-bearing rod 96. Flexible shaft 43 is brought into a flexible shaft adapter 181 through a spacer 182; and, by means of a coupling 183, a pin 184 and a shaft collar and thrust washer 185, shaft 43 is attached to the drive shaft 186 which is associated with the worm gear 179. Connection between the worm gear 179 and shaft 186 is controlled through magnetic clutch 187. In a similar fashion the flexible shaft 44 is brought into a flexible shaft adapter 191 through a spacer 192 and, by means of a coupling 193, pin 194 and a shaft collar and thrust washer 195, it is attached to the drive shaft 196 which is associated with the worm gear 180. Connection between the worm gear 180 and shaft 196 is controlled through a magnetic clutch 197. Shafts 186 and 196 are aligned and supported through suitable bearing systems such as 198 and 199 located within and supported by a drive housing 205 which is preferably integral with the drive support 206 and has cover plates 207.

When it is desired to move the load-bearing rods 95 and 96 in the high-speed mode, the high-speed motor 42 is employed to drive the pulley shaft 210 through the pulley system 53 by means of belt 211. As will be explained below in connection with FIG. 17, when the high-speed motor 42 is engaged for the high-speed drive mode, an electric switch in parallel with the high-speed motor engagement switch actuates the magnetic clutch 175 to cut out shaft 52 and the low-speed drivingmechanisms. When the pulley shaft 210 is coupled to the drive shaft 178 the mechanism by which the flexible shafts are driven through the bevel gear drive is the same as in the slowdriving or crystal-growing mode. Pulley shaft 210 rotates within a bearing system 212 which is mounted in bearing support 213.. The high-speed motor 42 is mounted on a motor support 214 in proper alignment to provide direct drive through the pulley 53 of the shafts 210 and 178.

FIGS. 9-11 illustrate in detail the mechanisms by which the lower load-bearing rod 96 is given rotational and translational motion and the manner in which this mechanism is connected to flexible shaft 44. The mechanism illustrated in these figures is essentially the same as that which is disclosed in U.S. Pat. application Ser. No. 653,478 filed July 14, 1967 in the names of Paul R. Doherty and Thomas P. I-Iosmer, now U.S. Pat. No. 3,552,931, and assigned to the same assignee as the subject application.

Turning first to FIG. 9 it will be seen that this drawing illustrates in an inverted view the main elements which make up the translation and rotational driving system associated with the lower rod 96 and hence which are connected to flexible shaft 44 (FIG. 8). The flexible shaft 44 extending from the driving mechanism illustrated in FIG.,8 is coupled to a driving worm 220 through a coupling 221 and a flexible shaft attachment 222. The driving worm 220 in turn engages the translational driving means generally indicated by the number 223. It will be seen that this comprises a vertical driving screw 224 which terminates in a lower 'clamp assembly 225. The thermocouple wires 115 and 116 which extend up through the lower shaft (FIGS. 7 and 13) exit at the bottom of clamp assembly 225 (FIG. 12) for attachment to their associated electronic equipment. As will be explained below the vertical drivescrew does not itself rotate but experiences only translational motion. This in turn requires that the rotation be achieved by a rotary spur gear 227 attached to the lower pulling head shaft by clamp assembly 228 which is mounted on rod 96 and which is in turn driven by rotary drive motor 39 through a shaft 229 which terminates in a driving gear 230. This driving gear 230 in turn engages the driven gear 23] mounted on shaft 232 which has affixed to it a rotary drive pinion shaft 233. v

y The rod actuating assembly may not be described in detail with references to FIGS. 10, 11 and 12. It is the purpose of the lower rod clamp assembly generally indicated. by the number 225 and shown in detail in FIG. 12 to affix the load-bearing rod 96 to the drivescrew 240 so that the rod 96 may rotate within the drivescrew 240 which does not itself rotate but which imparts only translational motion to the rod 96. This lower clamp assembly 225 comprises a thrust bearing 241 which is held in a thrust bearing housing 242 by means of a snap ring 243. A bushing 244 is provided at the upper end of the drivescrew 240. The rod and clamp assembly are free to rotate in the bushing 244 and in the drivescrew which expen'ences only translational motion.

Translational motion is imparted to the load-bearing rod 96 through the mechanism generally indicated by the numeral 223 (FIG. In the achievement of the translational motion as explained above the drivescrew assembly does not rotate. Rather, thethreaded nut 245 which engages the threads of the vertical drivescrew 240 rotates in the bushing 239 and this is accomplished by virtue of its connection, through a shoulder 246, to a worm wheel 247 which in turn is driven by the worm 220. This rotating assembly is mounted between an upper thrust washer 248 and a lower thrust washer 249 which is maintained in position through a thrust plate 250. Reference to FIG. 11 will show that this thrust plate 250 is attached through shoulder screws 25] to the casting which forms the housing 252, enclosing the driving mechanism. Through this attachment tension loads on the load-bearing rod 96 are transmitted to the casting through screws 251.

Returning to FIG. 10, it will be seen that the top end of the drive screw 240 is affixed to an antirotate plate 255 which in turn is affixed to the antirotate arm 2S6 engaging the antirotate shaft 257. At the top terminus of the drivescrew there is a bushing 258 in which the rod 96 rotates. The spur gear 227 for rotating the rod is mountedon the shaft through a clamp 228, a pin 260 and a thrust bearing 261 held in place by means of a snap ring 262.

The worm drive adapter assembly 263 for translational motion is shown in the cross section of FIG. 11 The worm 220 is affixed to work shaft 264 which is mounted in the main housing 252 through a forward shaft mount 265 and a flanged bushing 266, and an after shaft mount 267 (attached to the backplate 268 of the housing) and a flanged bushing 269.'The shaft 264 has an extension 222 adapted for attachment to the flexible shaft 44 (see FIG. 9) and the after mount 267 has a threaded section 270 which is adapted for attachment through a threaded collar 221 (FIG. 9) for making the proper connection with the flexible shaft casing.

The rotary drive adapter assembly is also shown in detail in the cross section of FIG. 11. It is generally indicated by the numeral 275. The driving bevel gear 230 is mounted on a shaft 276 which is retained in a shaft mount 281 fixed to the backplate 268 of housing 252. A forward flanged bushing 277 and an after flanged bushing 278 are provided for the shaft 276. A suitable adapter piece 279 is attached to'the end of the shaft and is designed to join shaft 276 with shaft 229 (FIG. 9)

Y which is associated with the rotary drive motor 39. Finally, it

will be seen that the housing has in addition to the backplate 268 a removable front plate 280 which completes the housing.

FIG. 10 (as well as FIG. 7) also illustrates in detail the manner which a pressure seal is effected around rod 96 as it experiences translational and rotational motions. The bushing housing shown generally in FIG. 7 as numeral 285 will be seen to comprise an adapter piece 286 in which there is located a bushing 287 furnishing the necessary alignment for the rod 96 as it extends beyond the top of housing 252. The adapter piece 286 is arranged to be connected with the lower section 92 of the furnace housing of FIG. 7. For this purpose there is provided an annular groove 288 which is suitable for retaining an O-ring 289. Y

The adapter piece 286 contains a gland seal generally indicated by the numeral 290. This seal comprises a body piece 291, an O-ring 292 which contacts the surface of rod 96, an O- ring 293 which seals the gland body to the adapter piece 290, a felt wiper 294, and a metallic wiper ring 295. The gland assembly is threaded into adapter piece 286 and the wipers are held in place by a snapring 296. The end of the gland body terminates in a hexagonal member 297. When the pulling head assembly is attached to the furnace 15 through screws 298 (FIG. 7) a fluidtight seal with inner volume 93 is achieved through O-ring seals 289 and 293. The rod must,.of course, rotate and move while retaining this fluidtight condition within the furnace and the O-ring seal 292 makes this possible. The gland assembly is designed to resist the pressure of the friction forces which must be overcome when the rod is moved. It is also designed to be easily and quickly removable for cleaning or replacement of O-rings.

The rotary drive pinion 233 and its associated shaft 232 are retained in position within the housing and mounted therein through a flanged bushing 305 which is positioned within a section 306 of the housing top. A fine pitch adjustment screw 307 and a suitable setscrew 308 are provided for axial adjustment of the pinion shaft in order to obtain proper bearing clearances. An electrical connection opening (not shown) is provided in the housing for passing through the necessary electrical lines for travel-limiting microswitches as shown generally at 315. The microswitches 315 (both upper and lower) are actuated by antirotate arm 257.

The lower portion of the lower pulling rod 96 extends into a dust cover 322 which is affixed to the housing 252 through collar 323 and which terminates in an end piece 324.

The driving mechanism associated with upper load-bearing rod 95 is identical to that associated with the lower load-bearing rod 96 and illustrated in FIG. 9--1I. FIG. 7 illustrates the attachment of this upper driving mechanism to the furnace and like reference numerals are used to identify like components. Upper rod 95 is, however, constructed to be cooled, and this therefore requires some modification in the rod as well as means to inject and withdraw a liquid coolant, e.g., water.

FIG. 14 shows the uppermost section of the upper loadbearing rod 95 in detail and illustrates these modifications. in the rod as well as the means for cooling the pulling rod 95. A dust cover 325 affixed to main shaft housing 252 (FIG. 7), is closed with a metallic cap 326 which snaps down over its top and provides the housing for the upper rod 95. In order tocool the rod 95 it is necessary to be able to direct a fluid coolant down through the rod and then return it for discharge. To do this there is provided a gland body 327 surrounding the upper portion of the rod and tightly sealed thereto through an upper O-ring 328, a weld 329 and a lower Q-ring 330. The gland body 327 is affixed to the drive screw 240 over a neck portion 331 of the drivescrew. The rod itself is formed of an outer tubing 335 and an inner tubing 336, the latter having internal thereof an inner coolant passage 337. The outer tubing 335 and the inner tubing 336 define between then an annular outer coolant passage 338. The passage 338 is closed at the terminal end of the inner tubing 336 by means of a suitable plug 339. Above the plug 339 and defined within the outer tubing 335 is an inlet coolant chamber 340 which is in fluid communication with an upper annular groove 341 defining a fluid passage and connected to the chamber by means of a series of ports 342. The annular passage 341 in turn is in fluid communication with an inlet conduit 344 which is in turn, through a suitable coupling, connected to an inlet water tubing 345 terminating in a quick disconnect 346.

In a similar manner the outer tubing 335 has ports 350 which provide fluid communication between the annular space 338 and an annular groove defining a passage 351. This latter passage is in turn connected through an outlet water conduit 352 to an outlet tube 353 which in turn is connected to a quick disconnect 354. At the bottom end of the cooled rod 95 there is placed a solid plug 355 which in effect closes both the inner coolant passage 337 and the outer coolant passage 338. Communication between these two is through ports 356.

In operation water or other coolant is introduced through tubing 345 and passes by way of chamber 340 into the inner water passage defined by the inner tubing 336. At the end of the rod the cooling water is transferred through ports 356 into the outer water passage 338 and returned via this passage, ports 350, annular passage 351, and conduit 352 into outlet tubing 353. As the rod 95 is moved up and down the inlet and outlet conduits 344 and 352 move within the elongated opening 357 in dust cover 325.

In operating the furnace it is very desirable for the operator to know at all times the precise position of the load-bearing rod or rods which are being used. A continuous rod-position readout system is therefore associated with each of the loadbearing rods 95 and 96, the one associated with the lower rod 96 being shown in FIG. 16. An identical system is associated with upper rod 95. This readout system is integrated into the vertical drive system of FIG. 9 and like numerals are used to identify like components in FIGS. 9 and 16. Extending beyond the vertical drive worm 220 and affixed thereto is a shaft 365 which has a magnet 366 attached at its end and along one side of it. The shaft 365 and its magnet rotates in a switch system 367 having a magnetic reed switch 368 positioned on one side of the shaft. The magnetic reed switch is electrically connected to the central terminal of portion 369 of a wafer switch (having another portion 370) and to a reversible electromagnetic counter set to record the distance traveled by the rod 96 from its bottommost position in hundredths of inches. The connections between the reversible counter and the DC motor control 372 and the wafer switch 369/370 are such as to register the addition of shaft 365 turns as rod 96 moves upwardly and to register the subtraction of shaft 365 turns as rod 96 moves downwardly. Thus the counter always records the precise position of the rod no matter in which direction the rod moves. This precise positioning is made possible by the worm gear ratio and thread pitch such that rod 96 moves l inch while shaft 365 turns I00 revolutions.

It is also, of course, within the scope of this invention to increase the sensitivity of the position determining device by increasing the number of magnets mounted on shaft 365 as well as to adapt the device to register in metric units.

In crystal growing, precise temperature control of the crystal forming melt in the crucible 97 is necessary. This is done automatically by the mechanism diagrammed in FIG. 17. The light pipe 120, which extends between the RF coil to within very close proximity of the surface of the graphite susceptor 97 is connected to a radiamatic pyrometer 375 which in turn is connected to a proportional temperature control system 376, such as a Leeds and Northrup HAZAR recorder or CAT Electric controller, which processes the DC signals received and transmits them, via a magnetic amplifier 377, in the form of an amplified signal to a saturable core reactor 378 which controls the amount of current transmitted to the induction heating power supply 379. Thus, by setting the temperature control system 376 at the desired temperature the amount of power delivered to the RF coil 125 is controlled and the temperature is maintained at the desired level. A pyrometer 385 may be connected to thermocouple junction 117 which gives a direct reading of temperature to the operator.

FIG. 18 illustrates in diagrammatic fashion the mechanisms which control the speed and direction of the rotational and translational motions of the load-bearing rods and 96. In the description of FIG. 18 reference should also be had to FIG. 8 which illustrates the synchronous drive assembly. In FIG. 18, like reference numerals are used to identify like components. The DC motor control 372 serves as the means for controlling the direction and rate at which rods 95 and 96 are moved; while the multispeed gear system 41 serves as the means for controlling the rate of translational motion in the slow or crystal-growing mode. As noted in connection with the description of FIG. 8, clutches 187 and 197 provide the means for choosing which rod is to be used. It is, of course, possible to use both rods such as in the zone-melting crystal growing technique. Clutch 187 is engaged and disengaged by closing and opening switch 385 which connects clutch 187 with its associated power supply 386. The power supply is in turn connected to the upper and lower limit switches 315 (see FIG. 10). In like manner clutch 197 is engaged and disengaged by closing and opening switch 388 which connects clutch 197 with its associated power supply 389. Like rod 95, the travel limits of rod 96 are controlled by limit switches 315.

In order to insure that the rods are driven either in the slow or in the rapid mode and that if one is cut in the other is cut out, a common supply of AC power is provided for both the high-speed motor 42 and the magnetic clutch 175. A switch system 390 makes it impossible for current to be supplied simultaneously to the clutch 175, through the DC clutch power supply 391, and to the high-speed motor 42. When the apparatus is operating in its slow, cyrstal-growing mode, the high-speed motor idles.

Finally, motors 38 and 39 which rotate the rod are controlled through their respective motor controls 392 and 393 which determine both direction and speed of rotation.

The apparatus of this invention provides a completely integrated system for growing crystals or for related operations where pressure and temperature must be accurately controlled. The operations performed within the furnace may be carried out and monitored by an operator located remote from the actual furnace. Complete information as to the operation including the precise position of the load-bearing rods and their loads is continuously available to the operator.

vided for permitting only one mode to be actuated at any one time.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim: I

l. A pressureand temperature-controlled apparatus adapted for growing crystals and the like, comprising in combination.

a. a pressuretight enclosure defining a therein;

b. upper and lower load-bearing rods extending through pressuretight bushing means into said volume and movable therein in both rotational and translational modes;

. upper and lower rotational and translational rod driving means located external of said pressuretight enclosure, said translational driving means including means to selectively drive said rods in a slow crystal-growing mode or in a rapid-positioning mode;

d. rod-locating means associated with said translational driving means adapted continuously to indicate the precise position of said rods within said volume;

e. heating means positioned with respect to said rods to heat a load supported by one or both of said rods within aid volume; and

f. viewing port means providing for visual observation of said load.

2. An apparatus according to claim 1 wherein said pressuretight enclosure has a hinged access port equipped with pressure-relief valve means.

- 3. An apparatus according to claim 1 wherein said pressuretight enclosure includes external cooling means in the working volume form of coils adapted to circulate a fluid coolant.

4. An apparatus according to claim 1 wherein said pressuretight enclosure has associated therewith a self-resetting pressure-relief valve and a solenoid-actuated relief valve.

5. An apparatus according to claim 1 wherein said upper load-bearing rod incorporates fluid channels therein adapted to circulate a fluid coolant therethrough.

6. An apparatus according to claim 1 wherein said lower load-bearing rod serves as a housing for a thermocouple junction placed internally thereof at its upper end and for thermocouple lead wires.

7. An apparatus according to claim lwherein said translational driving means associated with each rod comprises in combination 1. a vertical driving screw in which said rod rotates,

2. worm drive means for actuating said driving screw,

3. flexible drive shaft means connected to said worm drive means,

4. motor means connected through multispeed gear means, first clutch means, bevel gear means and second clutch means to said flexible drive shaft means,

5. a high-speed motor connected through said bevel gear means and said second clutch means to said flexible drive shaft means,

6. first clutch-engaging means having energizing means connected to a current supply means common to said high- ,speed motor through switch means adapted to supply current to either said first clutch-engaging means or said high-speed motor but not to both simultaneously, and

7. second clutch-engaging means.

8. An apparatus according to claim 7, wherein said rodlocating means comprises, in combination 1. a shaft extension on said worm drive means,

2. a magnet attached along the side of said shaft extension,

3. magnetic reed switch means actuatable by said magnet,

4. a reversible electromagnetic encounter, and

5. switch means connecting said reed switch means and said counter,'said switch means being arranged to actuate said counter to register turns of said shaft extension in terms of the exact linear distance the end of said rod is from a fixed reference point.

9. An apparatus according to claim 1 wherein said heating means is an RF coil.

, 10. An apparatus according to claim I wherein said heating means is an RF coil and has associated therewith temperature monitoring and controlling means, comprising in combination 1. light pipe means,

2. a radiamatic pyrometer connected to said light pipe means and adapted to generate DC voltage signals proportional to the light received,

3. induction heating power supply means for said RF coil,

4. a saturable core reactor adapted to control current input into said power supply means, and

5. voltage signal processing means adapted to amplify said voltage signals for transmission to aid saturable core whereby said core in controlling said current input controls the temperature developed by said RF coil.

11. An apparatus according to claim 1 wherein said viewing port means comprises a tempered Pyrex window protected within said enclosure by an infrared-reflecting window and having an external, rotatably mounted cross-polarizer to control the intensity of the image transmitted through-said windows.

12. An apparatus according to claim 1 including valvedcontrolled gas inlet means extending through the housing of said viewing port means and positioned to direct incoming gas against the window system in said viewing port means thereby to provide means to clean said window system.

13. An apparatus according to claim 1 including a television camera positioned adjacent one of the windows of said viewing port means and television-receiving means located remotely from said pressuretight enclosure.

14. A pressureand temperature-controlled apparatus adapted for growing crystals and the like, comprising in combination a. a pressuretight enclosure defining a working volume therein and having a hinged access port equipped with pressure-relief valve means;

. external cooling means for said pressuretight enclosure adapted to circulate a fluid coolant;

upper and lower load-bearing rods extending through pressuretight bushing means into said volume and movable therein in both rotational and translational modes;

. upper and lower rotational and translational rod driving means located external of said pressuretight enclosure,

said translational driving means comprising, in combination 1. a vertical driving screw in which said rod rotates,

2. worm drive means for actuating said driving screw,

3. flexible drive shaft means connected to said worm drive means,

4. motor means connected through multispeed gear means, first clutch means, bevel gear means and second clutch means to said flexible drive shaft means,

5. a high-speed motor connected through said bevel gear means and said second clutch means to said flexible drive shaft means,

6. first clutch engaging means having energizing means connected to a current supply means common to said high-speed motor through switch means adapted to supply current to either said first clutch engaging means or said high-speed motor but not to both simultaneously, and

7. second clutch engaging means;

rod-locating means associated with said translational driving means adapted continuously to indicate the precise position of said rods within said volume and comprising, in combination 1. a shaft extension on said worm drive means of said roddriving means,

2. a magnet attached along the side of said shaft extenslon,

3. reed switch means actuatable by said magnet,

4. a reversible electromagnetic counter, and

5. switch means connecting said reed switch means and said counter, said switch means being arranged to actuate said counter to register turns of said shaft extension in terms of the exact linear distance the end of said rod is from a fixed reference point;

f. RF coil heating means positioned with respect to said rods to heat a load supported by one or both of said rods within said volume, and having temperature monitoring and controlling means associated with said RF coil which comprise 1. light pipe means,

2. a radiamatic pyrometer connected to said light pipe means and adapted to generate DC voltage signals proportional to the light received,

3. induction heating power supply means for said RF coil,

4. a saturable core reactor adapted to control current input into said power supply means, and

5. voltage signal processing means adapted to amplify said voltage signals for transmission to said saturable core whereby said core in controlling said current input controls the temperature developed by said RF coil;

g. viewing port means providing for observation of said load and comprising at least one tempered Pyrex window protected within said enclosure by an infrared-reflecting window and having an external rotatably mounted crosspolarizer to control the intensity of the image transmitted through said windows;

h. valved-controlled gas inlet means extending through the housing of said viewing port means and positioned to direct incoming gas against the window system in said viewing port means; and

i. valved-controlled evacuating means adapted to produce a vacuum within said volume.

15. An apparatus according to claim 14 wherein said upper load-bearing rod incorporates fluid channels therein adapted to circulate a fluid coolant therethrough.

16. An apparatus according to claim 14 wherein said lower load-bearing rod serves as a housing for a thermocouple junction placed internally thereof at its upper end and for thermocouple lead wires.

17. An apparatus according to claim 14 including a television camera positioned to view the working volume within said enclosure and a television receiving means remote from said camera.

18. An apparatus according to claim 14 including a selfresetting pressure-relief valve and a solenoid-actuated relief valve associated with said pressuretight enclosure.

19. An apparatus according to claim 14 wherein control means for said rod driving means, rod-locating means, said RF coil heating means, said valve-controlled gas inlet means and said valve-controlled evacuating means are located remote from said pressuretight enclosure whereby the entire operation performed within said work volume may be monitored and controlled at a location remote from said pressuretight enclosure.

20. An apparatus according to claim 14 wherein said viewing port means comprises a primary viewing port and an auxiliary viewing port, each of which comprises a tempered Pyrex window, an infrared-reflecting window and a crosspolarizer. 

1. A pressure- and temperature-controlled apparatus adapted for growing crystals and the like, comprising in combination. a. a pressuretight enclosure defining a working volume therein; b. upper and lower load-bearing rods extending through pressuretight bushing means into said volume and movable therein in both rotational and translational modes; c. upper and lower rotational and translational rod driving means located external of said pressuretight enclosure, said translational driving means including means to selectively drive said rods in a slow crystal-growing mode or in a rapidpositioning mode; d. rod-locating means associated with said translational driving means adapted continuously to indicate the precise position of said rods within said volume; e. heating means positioned with respect to said rods to heat a load supported by one or both of said rods within aid volume; and f. viewing port means providing for visual observation of said load.
 2. An apparatus according to claim 1 wherein said pressuretight enclosure has a hinged access port equipped with pressure-relief valve means.
 2. worm drive means for actuating said driving screw,
 2. a radiamatic pyrometer connected to said light pipe means and adapted to generate DC voltage signals proportional to the light received,
 2. a magnet attached along the side of said shaft extension,
 2. worm drive means for actuating said driving screw,
 2. a radiamatic pyrometer connected to said light pipe means and adapted to generate DC voltage signals proportional to the light received,
 2. a magnet attached along the side of said shaft extension,
 3. reed switch means actuatable by said magnet,
 3. induction heating power supply means for said RF coil,
 3. flexible drive shaft means connected to said worm drive means,
 3. magnetic reed switch means actuatable by said magnet,
 3. induction heating power supply means for said RF coil,
 3. flexible drive shaft means connected to said worm drive means,
 3. An apparatus according to claim 1 wherein said pressuretight enclosure includes external cooling means in the form of coils adapted to circulate a fluid coolant.
 4. An apparatus according to claim 1 wherein said pressuretight enclosure has associated therewith a self-resetting pressure-relief valve and a solenoid-actuated relief valve.
 4. motor means connected through multispeed gear means, first clutch means, bevel gear means and second clutch means to said flexible drive shaft means,
 4. a saturable core reactor adapted to control current input into said power supply means, and
 4. a reversible electromagnetic encounter, and
 4. motor means connected through multispeed gear means, first clutch means, bevel gear means and second clutch means to said flexible drive shaft means,
 4. a saturable core reactor adapted to control current input into said power supply means, and
 4. a reversible electromagnetic counter, and
 5. switch means connecting said reed switch means and said counter, said switch means being arranged to actuate said counter to register turns of said shaft extension in terms of the exact linear distance the end of said rod is from a fixed reference point; f. RF coil heating means positioned with respect to said rods to heat a load supported by one or both of said rods within said volume, and having temperature monitoring and controlling means associated with said RF coil which comprise
 5. voltage signal processing means adapted to amplify said voltage signals for transmission to said saturable core whereby said core in controlling said current input controls the temperature developed by said RF coil; g. viewing port means providing for observation of said load and comprising at least one tempered Pyrex window protected within said enclosure by an infrared-reflecting window and having an external rotatably mounted cross-polarizer to control the intensity of the image transmitted through said windows; h. valved-controlled gas inlet means extending through the housing of said viewing port means and positioned to direct incoming gas against the window system in said viewing port means; and i. valved-controlled evacuating means adapted to produce a vacuum within said volume.
 5. a high-speed motor connected through said bevel gear means and said second clutch means to said flexible drive shaft means,
 5. switch means connecting said reed switch means and said counter, said switch means being arranged to actuate said counter to register turns of said shaft extension in terms of the exact linear distance the end of said rod is from a fixed reference point.
 5. voltage signal processing means adapted to amplify said voltage signals for transmission to aid saturable core whereby said core in controlling said current input controls the temperature developed by said RF coil.
 5. a high-speed motor connected through said bevel gear means and said second clutch means to said flexible drive shaft means,
 5. An apparatus according to claim 1 wherein said upper load-bearing rod incorporates fluid channels therein adapted to circulate a fluid coolant therethrough.
 6. An apparatus according to claim 1 wherein said lower load-bearing rod serves as a housing for a thermocouple junction placed internally thereof at its upper end and for thermocouple lead wires.
 6. first clutch-engaging means having energizing means connected to a current supply means common to said high-speed motor through switch means adapted to supply current to either said first clutch-engaging means or said high-speed motor but not to both simultaneously, and
 6. first clutch engaging means having energizing means connected to a current supply means common to said high-speed motor through switch means adapted to supply current to either said first clutch engaging means or said high-speed motor but not to both simultaneously, and
 7. second clutch engaging means; e. rod-locating means associated with said translational driving means adapted continuously to indicate the precise position of said rods within said volume and comprising, in combination
 7. second clutch-engaging means.
 8. An apparatus according to claim 7, wherein said rod-locating means comprises, in combination
 7. An apparatus according to claim 1 wherein said translational driving means associated with each rod comprises in combination
 9. An apparatus according to claim 1 wherein said heating means is an RF coil.
 10. An apparatus according to claim 1 wherein said heating means is an RF coil and has associated therewith Temperature monitoring and controlling means, comprising in combination
 11. An apparatus according to claim 1 wherein said viewing port means comprises a tempered Pyrex window protected within said enclosure by an infrared-reflecting window and having an external, rotatably mounted cross-polarizer to control the intensity of the image transmitted through said windows.
 12. An apparatus according to claim 1 including valved-controlled gas inlet means extending through the housing of said viewing port means and positioned to direct incoming gas against the window system in said viewing port means thereby to provide means to clean said window system.
 13. An apparatus according to claim 1 including a television camera positioned adjacent one of the windows of said viewing port means and television-receiving means located remotely from said pressuretight enclosure.
 14. A pressure- and temperature-controlled apparatus adapted for growing crystals and the like, comprising in combination a. a pressuretight enclosure defining a working volume therein and having a hinged access port equipped with pressure-relief valve means; b. external cooling means for said pressuretight enclosure adapted to circulate a fluid coolant; c. upper and lower load-bearing rods extending through pressuretight bushing means into said volume and movable therein in both rotational and translational modes; d. upper and lower rotational and translational rod driving means located external of said pressuretight enclosure, said translational driving means comprising, in combination
 15. An apparatus according to claim 14 wherein said upper load-bearing rod incorporates fluid channels therein adapted to circulate a fluid coolant therethrough.
 16. An apparatus according to claim 14 wherein said lower load-bearing rod serves as a housing for a thermocouple junction placed internally thereof at its upper end and for thermocouple lead wires.
 17. An apparatus according to claim 14 including a television camera positioned to view the working volume within said enclosure and a television receiving means remote from said camera.
 18. An apparatus according to claim 14 including a self-resetting pressure-relief valve and a solenoid-actuated relief valve associated with said pressuretight enclosure.
 19. An apparatus according to claim 14 wherein control means for said rod driving means, rod-locating means, said RF coil heating means, said valve-controlled gas inlet means and said valve-controlled evacuating means are located remote from said pressuretight enclosure whereby the entire operation performed within said work volume may be monitored and controlled at a location remote from said pressuretight enclosure.
 20. An apparatus according to claim 14 wherein said viewing port means comprises a primary viewing port and an auxiliary viewing port, each of which comprises a tempered Pyrex window, an infrared-reflecting window and a crosspolarizer. 